Progression and Regression of Hepatic Lesions in a Mouse Model of NASH Induced by Dietary Intervention and Its Implications in Pharmacotherapy

Abstract

Understanding of the temporal changes of hepatic lesions in the progression and regression of non-alcoholic steatohepatitis (NASH) is vital to elucidation of the pathogenesis of NASH, and critical to the development of a strategy for NASH pharmacotherapy. There are challenges in studying hepatic lesion progression and regression in NASH patients due to the slow development of NASH in humans, one being the requirement for multiple biopsies during the longitudinal follow-up. Here we studied lesion progression and regression in the diet-induced animal model of NASH by application or removal of the pathogenic diet for multiple time periods. Male C57BL/6 mice fed Western diet developed progressive hepatic steatosis/macrovesicular vacuolation, inflammation, and hepatocyte degeneration, as well as perisinusoidal fibrosis and occasionally portal fibrosis as early as 2 months after initiation of the Western diet. In the same period, the mice exhibited elevated ALT (alanine aminotransferase) and AST (aspartate aminotransferase) enzyme activities, CK18 (cytokeratin−18), PIIINP (N-terminal propeptide of type III collagen), and TIMP-1 (tissue inhibitor of metalloproteinase−1). Hepatic steatosis diminished rapidly when the Western diet was replaced by normal rodent chow diet and hepatic inflammation and hepatocyte degeneration were also reduced. Interestingly, perisinusoidal fibrosis and portal fibrosis regressed 8 months after chow diet replacement. To understand pharmacotherapy for NASH, mice with established NASH hepatic lesions were treated with either FXR agonist obeticholic acid (Ocaliva), or CCR2/5 antagonist Cenicriviroc. Similar to the diet replacement, metabolic modulator Ocaliva markedly reduced steatosis/macrovesicular vacuolation, hepatic inflammation, and hepatocyte degeneration effectively, but exhibited no significant effect on liver fibrosis. Anti-inflammation drug Cenicriviroc, on the other hand, markedly decreased inflammation and hepatocyte degeneration, and mildly decreased liver fibrosis, but exhibited no effect on hepatic steatosis/macrovesicular vacuolation. In conclusion, we found the progression of NASH hepatic steatosis/macrovesicular vacuolation, and inflammation eventually lead to hepatocyte death and fibrosis. Life style change and current pharmacotherapies in development may be effective in treating NASH, but their effects on NASH–induced fibrosis may be mild. Since fibrosis is known to be an independent risk for decompensated cirrhosis, cardiovascular events, and mortality, our study suggests that effective anti-fibrosis therapy should be an essential component of the combined pharmacotherapy for advanced NASH.

Multi-omics characterization of a diet-induced obese model of non-alcoholic steatohepatitis

“…In the present study, we performed a comprehensive characterization of the molecular signature of a histologically validated diet-induced model of NASH. As previously reported [32][33][34][35][36][37] , the AMLN DIO-NASH model exhibits key hallmarks of NASH pathogenesis; steatosis, inflammation and moderate fibrosis. As in human liver pathologies, DIO-NASH mice are characterized by a large variation in disease progression and thus a careful validation of the phenotype is a prerequisite for the validity of omics data obtained from NASH animal cohorts.…”

Human translatability of the GAN diet-induced obese mouse model of non-alcoholic steatohepatitis

“…We have further refined and validated this diet formula, termed the Amylin liver NASH (AMLN) diet [12], for reliably inducing metabolic, biochemical and liver-biopsy confirmed histological changes recapitulating hallmarks of NASH in C57BL/6 J (AMLN DIO-NASH) and leptin-deficient ob/ob (AMLN ob/ob-NASH) mice. The two AMLN models have been increasingly used in preclinical drug development for NASH [12][13][14][15][16][17][18][19][20]. However, a recent regulatory ban on transfats as food additive [21] has prompted the development of a compatible Western diet capable of promoting metabolic and liver histopathological changes similar to the AMLN diet.…”

Withaferin A Improves Nonalcoholic Steatohepatitis in Mice

“…WA Improves HFD-Induced Liver Injury. In contrast to the MCD diet-induced NASH model that results in body weight loss and does not cause insulin resistance coincident with inducing steatohepatitis, the 40 kcal% HFD-induced obese NASH model is thought to better mimic the typical human NASH pathologies of insulin resistance, high serum lipid accumulation, and obesity (Hebbard and George, 2011;Griffett et al, 2015;Honda et al, 2016;Ding et al, 2018). To further confirm the effect of WA in treating NASH, the HFD regimen and its matched LFD were used to test the effect of WA both in preventing and therapeutically improving NASH.…”

“…In the obese NASH model, WA treatment improved NASH-associated pathologies, including hepatic steatosis, inflammation, and fibrosis, in a timedependent manner. Since HFD diet feeding causes hepatic steatosis and minor fibrosis after a 2-month diet feeding that gradually progress to advanced NASH (Ding et al, 2018), the effect of WA treatments for 12 weeks during the full course of HFD feeding would be mainly regarded as a preventive effect, whereas WA treatment for 8 and 4 weeks after the onset of NASH would evaluate the therapeutic effects. In addition to WA's effect in improving NASH, WA also decreased HFDinduced body weight gain, in agreement with its known antiobesity activity .…”